This video was taken by fellows at the Marine Biological Laboratory Science Journalism Fellowship. The fellows fertilized sea urchin eggs, and made beautiful videos and photos of cells dividing and growing in the earliest stages of life. See the rest at http://boingboing.net/2012/07/02/the-beginning-of-life.html

“Sperm Cell Toxicity Tests Using the Sea Urchin, Arbacia punctulata” (EPA, 2009). The methods illustrated in the video and described in this supplemental guide support the methods published in the U.S. Environmental Protection Agency’s (EPA’s) Short-term Methods for Estimating the Chronic Toxicity of Effluents and Receiving Waters to Marine and Estuarine Organisms, Third Edition (EPA, 2002a), referred to as the Saltwater Chronic Methods Manual. The video and this guide provide details on preparing for and conducting the test based on the expertise of personnel at the following
EPA Office of Research and Development (ORD) laboratories:
National Health and Environmental Effects Research Laboratory (NHEERL) – Atlantic Ecology Division in Narragansett, Rhode Island
NHEERL – Gulf Ecology Division in Gulf Breeze, Florida
National Exposure Research Lab (NERL) – Ecological Exposure Research Division (EERD) in
Cincinnati, Ohio
This guide and its accompanying video are part of a series of training videos produced by EPA’s Office of Wastewater Management. This Saltwater Series includes the following videos and guides:
“Mysid (Americamysis bahia) Survival, Growth, and Fecundity Toxicity Tests”
“Culturing Americamysis bahia”
“Sperm Cell Toxicity Tests Using the Sea Urchin, Arbacia punctulata”
“Red Algal (Champia parvula) Sexual Reproduction Toxicity Tests”
“Sheepshead Minnow (Cyprinodon variegatus) and Inland Silverside (Menidia beryllina) Larval Survival and Growth Toxicity Tests”
The Freshwater Series, released in 2006, includes the following videos and guides:
“Ceriodaphnia Survival and Reproduction Toxicity Tests”
“Culturing of Fathead Minnows (Pimephales promelas)”
“Fathead Minnow (Pimephales promelas) Larval Survival and Growth Toxicity Tests”
All of these videos are available through the National Service Center for Environmental Publications (NSCEP) at 800 490-9198 or [email protected]

Sea Urchin Embryonic Development (time lapse) Video
This series of video clips shows selected important events in sea urchin embryonic development. 1) The unfertilized egg is about 100 micrometers (µm) in diameter, similar to that of humans, and is surrounded by an extracellular layer called the vitelline layer. Upon fertilization by the first sperm, the vitelline layer becomes raised off the surface of the egg and hardens, forming the protective structure known as the fertilization envelope. All cleavages up to the blastula stage occur within this envelope. 2) During first cleavage, the nuclear envelope breaks down, and the duplicated chromosomes separate into two complete sets, followed by cytokinesis. In the two new cells, or blastomeres, you can clearly see the two new nuclei. 3) Second cleavage, progressing from 2 to 4 cells, is seen here. Cleavages will proceed synchronously, approximately every 30 minutes, passing through the morula stage (16-64 cells) when the cells are loosely attached to each other, up to the blastula stage (more than 128 cells). 4) The blastula stage is seen at the end of this clip. This stage is made up of a hollow ball of 1000 or so cells, arranged in a single-layered epithelium. The cells are tightly packed together, maintaining a space in the center called the blastocoel cavity. 5) At the beginning of gastrulation, a number of cells in the flattened "vegetal pole," shown here at the bottom of the embryo, move as individual cells into the blastocoel cavity. In this cavity the cells migrate around, fuse with each other in a ring, and begin secreting elements of the calcium carbonate skeleton of the embryo. Because these cells are the first to move as individual cells in the embryo, they are called the primary mesenchyme cells (PMCs). The remaining cells in the vegetal pole fill in the gaps, restoring a complete epithelial sheet. 6) While the PMCs are migrating around, archenteron formation, or formation of the embryonic digestive tract, begins. The first stage involves the pushing in of the vegetal pole to form a short, wide, blind-ended tube. 7) This tube then narrows and elongates by a process that includes extensive cell rearrangement. Following this elongation, a subset of cells (secondary mesenchyme cells) at the tip of the archenteron will extend processes that contact a specific site on the inside of the ectodermal wall and tow the archenteron toward that spot. The wall of the ectoderm will bend inward and fuse with the tip of the archenteron to form the mouth. The digestive tract will differentiate into an esophagus, a stomach, and an intestine, and the embryo will begin to feed. Four to 8 or 12 arms will extend, supported by internal skeletal elements. This feeding larva will float around in the plankton, eating algal cells, for 5 or 6 weeks, then will metamorphose into the adult form of the sea urchin.
Credit: Rachel Fink, editor, "A Dozen Eggs," Society for Developmental Biology

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A exciting story from sea urchin life. I added the sperm at 27 sec, and at 59 sec the envelope already started to form! Isn't that fantastic? This is the "real close-up" porn - under the microscope!
Fertilization of the sea urchins happen externally and the lifecycle is fast and predictable.
Оплодотворение яйцеклетки морского ежа. Сперматозоиды добавлены на 27-й секунде.
受精
私は27秒で精子を追加しました

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Fertilisation (also known as conception, fecundation and syngamy) is the fusion of gametes to initiate the development of a new individual organism.[1] In animals, the process involves the fusion of an ovum with a sperm, which eventually leads to the development of an embryo. Depending on the animal species, the process can occur within the body of the female in internal fertilisation, or outside (external fertilisation). The cycle of fertilisation and development of new individuals is called reproduction.
Sperm find the eggs via chemotaxis, a type of ligand/receptor interaction. Resact is a 14 amino acid peptide purified from the jelly coat of A. punctulata that attracts the migration of sperm.
After finding the egg, the sperm penetrates the jelly coat through a process called sperm activation. In another ligand/receptor interaction, an oligosaccharide component of the egg binds and activates a receptor on the sperm and causes the acrosomal reaction. The acrosomal vesicles of the sperm fuse with the plasma membrane and are released. In this process, molecules bound to the acrosomal vesicle membrane, such as bindin, are exposed on the surface of the sperm. These contents digest the jelly coat and eventually the vitelline membrane. In addition to the release of acrosomal vesicles, there is explosive polymerisation of actin to form a thin spike at the head of the sperm called the acrosomal process.
The sperm binds to the egg through another ligand reaction between receptors on the vitelline membrane. The sperm surface protein bindin, binds to a receptor on the vitelline membrane identified as EBR1.
Fusion of the plasma membranes of the sperm and egg are likely mediated by bindin. At the site of contact, fusion causes the formation of a fertilisation cone. Source of the article published in description is Wikipedia. I am sharing their material. Copyright by original content developers of Wikipedia.
Link- http://en.wikipedia.org/wiki/Main_Page

Here, five unfertilized sea urchin eggs have been microinjected with a calcium indicator (and a tiny oil droplet to mark injected eggs). Sperm binding to the egg initiates a signaling cascade that results in the release of calcium from intracellular stores. Calcium release begins at the point of sperm contact and propagates through the cell as a wave. One of the consequences of calcium release is exocytosis of cortical granules and elevation of the fertilization envelope. Eventually, calcium is reabsorbed back into intracellular stores.

Sea urchin embryo at blastula stage comport a peripheral epithelium of individually ciliated cells. Each cell possesses one cilium, difficult to visualize because of interference of neighbour cilia. At high magnification, the low depth of field of the 100X objective allows indivisualization of cilium and detailed record of its beating. The last part of the clip shows individual cell that can be detached experimentally.

This developmental biology lecture explains about the sea urchin development including the sea urchin fertilization, prevention of polyspermy and the blastula and gastrulation of sea urchin embryo to produce the adult sea urchin animal.
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This video was taken by fellows at the Marine Biological Laboratory Science Journalism Fellowship. The fellows fertilized sea urchin eggs, and made beautiful videos and photos of cells dividing and growing in the earliest stages of life. See the rest at http://boingboing.net/2012/07/02/the-beginning-of-life.html

This video was taken by fellows at the Marine Biological Laboratory Science Journalism Fellowship. The fellows fertilized sea urchin eggs, and made beautiful videos and photos of cells dividing and growing in the earliest stages of life. See the rest at http://boingboing.net/2012/07/02/the-beginning-of-life.html

Perturbation of gut bacteria induces a coordinated cellular immune response in the purple sea urchin larva. Eric CH Ho et al (2016), Immunology and Cell Biology http://dx.doi.org/10.1038/icb.2016.51
The purple sea urchin (Strongylocentrotus purpuratus) genome sequence contains a complex repertoire of genes encoding innate immune recognition proteins and homologs of important vertebrate immune regulatory factors. To characterize how this immune system is deployed within an experimentally tractable, intact animal, we investigate the immune capability of the larval stage. Sea urchin embryos and larvae are morphologically simple and transparent, providing an organism-wide model to view immune response at cellular resolution. Here we present evidence for immune function in five mesenchymal cell types based on morphology, behavior and gene expression. Two cell types are phagocytic; the others interact at sites of microbial detection or injury. We characterize immune-associated gene markers for three cell types, including a perforin-like molecule, a scavenger receptor, a complement-like thioester-containing protein and the echinoderm-specific immune response factor 185/333. We elicit larval immune responses by (1) bacterial injection into the blastocoel and (2) seawater exposure to the marine bacterium Vibrio diazotrophicus to perturb immune state in the gut. Exposure at the epithelium induces a strong response in which pigment cells (one type of immune cell) migrate from the ectoderm to interact with the gut epithelium. Bacteria that accumulate in the gut later invade the blastocoel, where they are cleared by phagocytic and granular immune cells. The complexity of this coordinated, dynamic inflammatory program within the simple larval morphology provides a system in which to characterize processes that direct both aspects of the echinoderm-specific immune response as well as those that are shared with other deuterostomes, including vertebrates.

Conceived in the open sea, tiny spaceship-shaped sea urchin larvae search the vast ocean to find a home. After this incredible odyssey, they undergo one of the most remarkable transformations in nature.
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Every summer, millions of people head to the coast to soak up the sun and play in the waves. But they aren’t alone. Just beyond the crashing surf, hundreds of millions of tiny sea urchin larvae are also floating around, preparing for one of the most dramatic transformations in the animal kingdom.
Scientists along the Pacific coast are investigating how these microscopic ocean drifters, which look like tiny spaceships, find their way back home to the shoreline, where they attach themselves, grow into spiny creatures and live out a slow-moving life that often exceeds 100 years.“These sorts of studies are absolutely crucial if we want to not only maintain healthy fisheries but indeed a healthy ocean,” says Jason Hodin, a research scientist at the University of Washington’s Friday Harbor Laboratories.
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Sea urchins reproduce by sending clouds of eggs and sperm into the water. Millions of larvae are formed, but only a handful make it back to the shoreline to grow into adults.
--- What are sea urchins?
Sea urchins are spiny invertebrate animals. Adult sea urchins are globe-shaped and show five-point radial symmetry. They move using a system of tube feet. Sea urchins belong to the phylum Echinodermata along with their relatives the sea stars (starfish), sand dollars and sea slugs.
--- What do sea urchins eat?
Sea urchins eat algae and can reduce kelp forests to barrens if their numbers grow too high. A sea urchin’s mouth, referred to as Aristotle’s lantern, is on the underside and has five sharp teeth. The urchin uses the tube feet to move the food to its mouth.
--- How do sea urchins reproduce?
Male sea urchins release clouds of sperm and females release huge numbers of eggs directly into the ocean water. The gametes meet and the sperm fertilize the eggs. The fertilized eggs grow into free-swimming embryos which themselves develop into larvae called plutei. The plutei swim through the ocean as plankton until they drop to the seafloor and metamorphosize into the globe-shaped adult urchins.
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Pygmy Seahorses: Masters of Camouflage | Deep Look
https://www.youtube.com/watch?v=Q3CtGoqz3ww
The Fantastic Fur of Sea Otters | Deep Look
https://www.youtube.com/watch?v=Zxqg_um1TXI
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#deeplook #seaurchin #urchins

Embryos of the purple sea urchin, Strongylocentrotus purpuratus, are shown in an accelerated time-lapse of fertilization and the first 15 hours of development. The stationary cells are eggs that did not fertilize.

In this video we have discussed about the fertilization in Sea Urchin. The Fertilization in Sea Urchin is driven by some chemical factors known as SAPs ( śpérm Activating Polypeptides ). The SAPs function is to guide the śperm towards the egg so that it can fertilize it.
The SAPs bind to the cell membrane receptors of śperm cell and mediates the signalling pathway which ultimately leads to the motility of the flagella as described in the video.
The fertilisation process is divided into 5 different steps :
1.Sperm Attraction : which involves Chemotaxis
2.Acrosomal Reaction : which involves interaction of sperm and Egg Jelly
3.Fusion of Egg and Sperm cell membrane .
4.Blocks to Polyspermy , where multiple sperms are blocked entry into the egg
5.Activation of egg metabolism.
Here we have discussed the Chemotaxis only.

As a young scientist, Catherine Mohr was on her dream scuba trip -- when she put her hand right down on a spiny sea urchin. While a school of sharks circled above. What happened next? More than you can possibly imagine. Settle in for this fabulous story with a dash of science.
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Fertilization in sea urchin- This developmental biology lecture explains about the fertilization process in sea urchin. It also explains the polyspermy prevention in sea urchin development.
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WELCOME TO TEACHING PATHSHALA!!
TOPIC-PREVENTION OF POLYSPERMY IN SEA URCHINS |FAST AND SLOW BLOCK OF POLYSPERMY |CSIR NET|DEVELOPMENTAL BIOLOGY
Fast block to polyspermy –The fast block to polyspermy is achieved by changing the electric potential of the egg plasma membrane. Egg cell membrane initially have negative charge. This Negative charge will attract the positively charged sperm. During the entry of a sperm, the influx of Na+ ion in egg from sea environment will take place by the opening of Na+ ion channel
The slow block to polyspermy-The eggs of sea urchins (and many other animals) have a second mechanism to ensure that multiple sperm do not enter the egg cytoplasm, which is also called cortical granule reaction. The fertilization envelope starts to form at the site of sperm entry and continues its expansion around the egg. As it forms, bound sperm are released from the envelope. This process starts about 20 seconds after sperm attachment and is complete by the end of the first minute of fertilization.
The fast block to polyspermy is transient, since the membrane potential of the sea urchin egg remains positive for only about a minute. This brief potential shift is not sufficient to prevent polyspermy, which can still occur if the sperm bound to the vitelline envelope are not somehow removed
ABOUT THIS CHANNEL ---This channel will have the syllabus wise lectures Video for CSIR-NET-Lifescience/GATE-Lifescience/BARC/ICMR-JRF/ICAR.
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VIDEOS FROM DEVELOPMENTAL BIOLOGY UNIT-CSIR NET
FERTILIZATION IN SEA URCHIN-CSIR NET | DEV BIO
https://youtu.be/kAzL7VGpKRY
C. elegans vulva formation (part-1)
https://youtu.be/ati-iJ9zWKM
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Each peripheral cell of a sea urchin embryo (blastula stage) possesses on cilium. At high magnification (100X objective), cilia are observed individually while beating by DIC microscopy with stroboscopic illumination. The last part of the clip shows the ciliary anchoring structure present in each cell.

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The final part of this series looking at three brilliant contemporary scientists features Sir Tim Hunt, awarded the Nobel Prize for his discovery of the mechanism of how cells divide - a discovery fundamental to the life and growth of every single creature on the planet, as well as a vital clue into the mystery of cancer.
Hunt recalls moments in his life that provided inspiration for his career as a scientist, from his father's intent scholarship which shaped his early methods to his mother's battle with cancer and the influence of this on his current position at Cancer Research UK.
In his own words, Hunt recounts the events that informed his discovery, from chance encounters to life-changing conversations and reveals his own opinions on the thought processes, both logical and emotional, that led to his extraordinary discovery.
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Homing in on Sea Urchin Eggs
Video: Resetting of Ca2+ signals in single moving sperm. A sperm cell is loaded with the Ca2+ indicator Fluo-4 AM and caged cGMP. The cell is repeatedly stimulated by releasing cGMP from its caged derivative with six consecutive UV flashes. After each flash, the [Ca2+]i rapidly decreases and rises anew. The recording was performed using an epifluorescent microscope (IX71). Frames were acquired at 30 frames/s using a back-illuminated EM CCD camera (DU-897D). Photolysis of caged compounds was achieved using a mercury lamp (U-RFL-T). The irradiation time was controlled by a mechanical shutter (VS25). Laser stroboscopic illumination (488-nm wavelength and 2-ms pulse) was achieved using an acousto-optical tunable filter (AA Opto-Electronic Company). The fluorescence was filtered by a 500-nm long pass filter (500 ALP; Omega Optical, Inc.). Superposition of the scale bar and flash number to the original video was performed using MATLAB, and editing was finalized using VideoStudio Pro X4 (Corel Corporation).
- Homing in on Sea Urchin Eggs
http://news.sciencemag.org/sciencenow/2012/09/scienceshot-homing-in-on-sea-urc.html?ref=hp
Reference
Temporal sampling, resetting, and adaptation orchestrate gradient sensing in sperm
Kashikar et al. 198 (6): 1075, September 17, 2012 JCB vol. 198 no. 6 1075-1091, doi: 10.1083/jcb.201204024
http://jcb.rupress.org/content/198/6/1075.abstract
Abstract
Sperm, navigating in a chemical gradient, are exposed to a periodic stream of chemoattractant molecules. The periodic stimulation entrains Ca2+ oscillations that control looping steering responses. It is not known how sperm sample chemoattractant molecules during periodic stimulation and adjust their sensitivity. We report that sea urchin sperm sampled molecules for 0.2--0.6 s before a Ca2+ response was produced. Additional molecules delivered during a Ca2+ response reset the cell by causing a pronounced Ca2+ drop that terminated the response; this reset was followed by a new Ca2+ rise. After stimulation, sperm adapted their sensitivity following the Weber--Fechner law. Taking into account the single-molecule sensitivity, we estimate that sperm can register a minimal gradient of 0.8 fM/µm and be attracted from as far away as 4.7 mm. Many microorganisms sense stimulus gradients along periodic paths to translate a spatial distribution of the stimulus into a temporal pattern of the cell response. Orchestration of temporal sampling, resetting, and adaptation might control gradient sensing in such organisms as well.